Dashboard API returns 500s if Crawler Service using self-signed certificate

[iamwillbar]

If the endpoint at CRAWLER_SERVICE_URL is using a self-signed (or otherwise untrusted) certificate then the dashboard will fail to perform any actions that require talking to the Crawler Service. The dashboard should support passing a list of CA certificates to request like is done here: https://github.com/Microsoft/ghcrawler/blob/develop/providers/queuing/rabbitQueueManager.js#L48.